That will stop working way sooner than you’d like. Freezing a browser isn’t tenable at all, not just for features websites are expecting but also security issues. There’s a reason every browser except Safari has a 6 weeks release cycle.

Firefox uses the Web Extensions standard, just like Chrome. There are minor differences here or there but largely the same, tech wise.

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions

Post number 3.492 complaining about Threads